Question

A ruby laser produces radiations of wavelengths, 662.6 nm in pulse duration are 10${}^{-6}$s. If the laser produces 0.39 J of energy per pulse, how many photons are produced in each pulse?

• A. $1.3\times {10}^9$
• B. $1.3\times {10}^{18}$
• C. $1.3\times {10}^{27}$
• D. $3.9\times {10}^{18}$

Answer 1

Answer: (B)

$1.3\times {10}^{18}$

Total energy of pulse, $E=n\frac{hc}{\lambda }$

$⟹n=\frac{E\lambda }{hc}$ $=\frac{0.39\times 662.6\times {10}^{-9}}{6.626\times {10}^{-34}\times 3\times {10}^8}$ $=1.3\times {10}^{18}$